Sulfide solid electrolyte material, battery, and method for producing sulfide solid electrolyte material

ABSTRACT

An object of the present invention is to provide a sulfide solid electrolyte material with favorable ion conductivity. In the present invention, the above object is achieved by providing a sulfide solid electrolyte material comprising a composition of LixSiyPzS1-x-y-z-wXw (0.37≤x≤0.40, 0.054≤y≤0.078, 0.05≤z≤0.07, 0≤w≤0.05, and X is at least one of F, Cl, Br, and I), characterized in that the sulfide solid electrolyte material has a crystal phase A having a peak at a position of 2θ=29.58°±1.00° in X-ray diffraction measurement using a CuKα ray, the sulfide solid electrolyte material does not have a crystal phase B having a peak at a position of 2θ=30.12°±1.00° in X-ray diffraction measurement using a CuKα ray, or slightly has the crystal phase B.

TECHNICAL FIELD

The present invention relates to a sulfide solid electrolyte materialwith favorable ion conductivity.

BACKGROUND ART

In recent years, with rapid spread of information-related equipment andcommunication equipment such as personal computers, video cameras, andmobile phones, the development of batteries used as a power sourcetherefor has been emphasized. Further, also in the automobile industryand other industries, the development of batteries having high outputand high capacity for electric vehicles or hybrid vehicles has beenadvanced. Among various batteries, a lithium battery has been presentlynoticed from the viewpoint of a high energy density.

A liquid electrolyte containing a flammable organic solvent is used fora presently commercialized lithium battery, so that the installation ofa safety device for restraining temperature rise during a short circuitand an apparatus for preventing a short circuit are necessary therefor.To the contrary, a lithium battery all-solidified by replacing theliquid electrolyte with a solid electrolyte layer is conceived to intendthe simplification of the safety device and be excellent in productioncost and productivity for the reason that the flammable organic solventis not used in the battery.

A sulfide solid electrolyte material has been known as a solidelectrolyte material used for an all solid lithium battery. For example,Patent Literature 1 discloses a LiSiPS-based sulfide solid electrolytematerial (argyrodite type). Further, for example, Patent Literature 2discloses a sulfide solid electrolyte material having a composition ofLi_((4-x))Ge_((1-x))P_(x)S₄.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Application Publication (JP-A)    No. 2013-137889-   Patent Literature 2: WO 2011/118801

SUMMARY OF INVENTION Technical Problem

A solid electrolyte material with favorable ion conductivity has beendemanded from the viewpoint of achieving higher output of a battery. Thepresent invention has been made in view of the above-described problems,and a main object thereof is to provide a sulfide solid electrolytematerial with favorable ion conductivity.

Solution to Problem

In order to solve the above-described problems, the present inventionprovides a sulfide solid electrolyte material comprising a compositionof Li_(x)Si_(y)P_(z)S_(1-x-y-z-w)X_(w) (0.37≤x≤0.40, 0.054≤y≤0.078,0.05≤z≤0.07, 0≤w≤0.05, and X is at least one of F, Cl, Br, and I),characterized in that the sulfide solid electrolyte material has acrystal phase A having a peak at a position of 2θ=29.58°±1.00° in X-raydiffraction measurement using a CuKα ray, the sulfide solid electrolytematerial does not have a crystal phase B having a peak at a position of2θ=30.12°±1.00° in X-ray diffraction measurement using a CuKα ray, or ina case where the sulfide solid electrolyte material has the crystalphase B, when a diffraction intensity at the peak of 2θ=29.58°±1.00° isdesignated as I_(A) and a diffraction intensity at the peak of2θ=30.12°±1.00° is designated as I_(B), a value of I_(B)/I_(A) is 0.6 orless.

According to the present invention, since the sulfide solid electrolytematerial comprises a specific composition, has the crystal phase A, anddoes not have the crystal phase B, or if the sulfide solid electrolytematerial has the crystal phase B, the crystal phase B is slightlycontained, it is possible to obtain the sulfide solid electrolytematerial with favorable ion conductivity.

In the above-described invention, it is preferable that the “w”satisfies 0<w≤0.05.

Further, in the present invention, there is provided a batterycomprising: a cathode active material layer containing a cathode activematerial; an anode active material layer containing an anode activematerial; and an electrolyte layer formed between the cathode activematerial layer and the anode active material layer, in which at leastone of the cathode active material layer, the anode active materiallayer, and the electrolyte layer contains the sulfide solid electrolytematerial described above.

According to the present invention, when the above-described sulfidesolid electrolyte material is used, it is possible to obtain ahigh-output battery.

Further, in the present invention, there is provided a method forproducing a sulfide solid electrolyte material, the sulfide solidelectrolyte material being the sulfide solid electrolyte materialdescribed above, the method comprising steps of: an ion conductivematerial synthesizing step of synthesizing an amorphized ion conductivematerial by mechanical milling while using a raw material compositioncontaining the constitutional component of the sulfide solid electrolytematerial; and a heating step of heating the amorphized ion conductivematerial to obtain the sulfide solid electrolyte material.

According to the present invention, a sulfide solid electrolyte materialwith favorable ion conductivity can be obtained by performingamorphization in the ion conductive material synthesizing step and thenperforming the heating step.

Advantageous Effects of Invention

The sulfide solid electrolyte material of the present invention exhibitsan effect of having favorable ion conductivity.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a four-dimensional diagram illustrating a compositional rangeof a sulfide solid electrolyte material of the present invention.

FIG. 2 is a perspective view describing an example of the crystallinestructure of a crystal phase A of the present invention.

FIG. 3 is a schematic cross-sectional view illustrating an example of abattery of the present invention.

FIG. 4 is an explanatory diagram illustrating an example of a method forproducing a sulfide solid electrolyte material of the present invention.

FIGS. 5A to 5C show an X-ray diffraction spectrum of the sulfide solidelectrolyte material obtained in each of Examples 7 and 41 andComparative Example 4.

FIGS. 6A and 6B show an X-ray diffraction spectrum of the sulfide solidelectrolyte material obtained in each of Examples 7 and 55.

FIG. 7 shows Li ion conductance of the sulfide solid electrolytematerial obtained in each of Examples 1 to 58 and Comparative Examples 1to 7.

FIG. 8 is a graph showing a relation between I_(B)/I_(A) and ionconductance in the sulfide solid electrolyte material obtained in eachof Examples 1 to 58 and Comparative Examples 1 to 7.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a sulfide solid electrolyte material, a battery, and amethod for producing a sulfide solid electrolyte material of the presentinvention will be described in detail.

A. Sulfide Solid Electrolyte Material

First, the sulfide solid electrolyte material of the present inventionwill be described. The sulfide solid electrolyte material of the presentinvention comprises a composition of Li_(x)Si_(y)P_(z)S_(1-x-y-z-w)X_(w)(0.37≤x≤0.40, 0.054≤y≤0.078, 0.05≤z≤0.07, 0≤w≤0.05, and X is at leastone of F, Cl, Br, and I), in which the sulfide solid electrolytematerial has a crystal phase A having a peak at a position of2θ=29.58±1.00° in X-ray diffraction measurement using a CuKα ray, thesulfide solid electrolyte material does not have a crystal phase Bhaving a peak at a position of 2θ=30.12°±1.00° in X-ray diffractionmeasurement using a CuKα ray, or in a case where the sulfide solidelectrolyte material has the crystal phase B, when a diffractionintensity at the peak of 2θ=29.58°±1.00° is designated as I_(A) and adiffraction intensity at the peak of 2θ=30.12°±1.00° is designated asT_(B), a value of I_(B)/I_(A) is 0.6 or less.

According to the present invention, since the sulfide solid electrolytematerial comprises a specific composition, has the crystal phase A, anddoes not have the crystal phase B, or if the sulfide solid electrolytematerial has the crystal phase B, the crystal phase B is slightlycontained, it is possible to obtain the sulfide solid electrolytematerial with favorable ion conductivity. Further, the ion conductivityis greatly influenced by a valence of an element forming the skeleton ofthe crystal phase and an ionic radius. In the composition in the presentinvention, since a skeleton suitable for Li ion conduction is formed andthe Li ion is less likely to be confined in the skeleton, it isconsidered that high ion conductivity is exerted. Further, the sulfidesolid electrolyte material of the present invention is a novel materialwhich has not conventionally been known. Incidentally, the compositionalrange of the sulfide solid electrolyte material of the present inventioncorresponds to a region A in FIG. 1. On the other hand, PatentLiterature 1 discloses a LiSiPS-based sulfide solid electrolyte materialand the compositional range thereof corresponds to a region B in FIG. 1.In this way, the compositional range in the present invention iscompletely different from the compositional range in Patent Literature1.

The sulfide solid electrolyte material of the present inventioncomprises a composition of Li_(x)Si_(y)P_(z)S_(1-x-y-z-w)X_(w)(0.37≤x≤0.40, 0.054≤y≤0.078, 0.05≤z≤0.07, 0≤w≤0.05, and X is at leastone of F, Cl, Br, and I). Incidentally, “x”, “y”, “z”, and “w” can beidentified by ICP.

“0.37≤x” in the above-described composition technically means 0.365≤x.That is, a value of “x” in the above determination means a value roundedat one lower place of a significant figure (in this case, at the thirddecimal place). In this regard, the same is applied to “y”, “z”, and“w”. “x” way satisfy 0.38≤x. Further, similar to the above description,“x≤0.40” technically means x≤0.404. “x” may satisfy x≤0.39.

“y” generally satisfies 0.054≤y, and may satisfy 0.056≤y or 0.058≤y. Onthe other hand, “y” generally satisfies y≤0.078 and may satisfy y≤0.076.Further, “z” generally satisfies 0.05≤z and may satisfy 0.055≤z. On theother hand, “z” generally satisfies z≤0.07 and may satisfy z≤0.065.Further, “w” generally satisfies 0≤w, and may satisfy 0<w, 0.01≤w, or0.02≤w. In the case of 0<w, a part of sulfur (S) is substituted withhalogen (X) and thus an influence of the interaction between sulfur andlithium can be reduced. Therefore, there is a possibility that Li ionconductivity is improved. On the other hand, “w” generally satisfiesw≤0.05 and may satisfy w≤0.04.

X in the above-described composition is generally at least one of F, Cl,Br, and I, above all, at least one of Cl and Br is preferable.

The sulfide solid electrolyte material of the present invention has acrystal phase A having a peak at a position of 2θ=29.58°±1.00° in X-raydiffraction measurement using a CuKα ray. The crystal phase A is thesame crystal phase of the LiGePS-based sulfide solid electrolytematerial described in Patent Literature 2 and has high ion conductivity.The crystal phase A generally has peaks at positions of 2θ=17.38°,20.18°, 20.44°, 23.56°, 23.96°, 24.93°, 26.96°, 29.07°, 29.58°, 31.71°,32.66°, and 33.39°. Incidentally, regarding these peak positions, acrystal lattice slightly changes due to factors such as the materialcomposition, and these peak positions occasionally shift in the range of±1.00°. Above all, each peak position is preferably in the range of±0.50°.

FIG. 2 is a perspective view describing an example of the crystallinestructure of the crystal phase A. The crystal phase A has an octahedronO composed of a Li element and a S element, a tetrahedron T₁ composed ofan M_(a) element and a S element, and a tetrahedron T₂ composed of anM_(b) element and a S element. The tetrahedron T₁ and the octahedron Oshare an edge, and the tetrahedron T₂ and the octahedron O have acrystalline structure sharing a corner. The M_(a) element and the M_(b)element each are at least one of a Si element and a P element. Further,there is a possibility that the S of the octahedron O and the tetrahedraT₁ and T₂ is substituted with halogen X.

The ratio of the crystal phase A contained in the sulfide solidelectrolyte material of the present invention relative to the totalcrystal phase is preferably larger. Specifically, the ratio of thecrystal phase A is preferably 50 wt % or more, more preferably 70 wt %or more, and further preferably 90 wt % or more. Incidentally, the ratioof the crystal phase can be measured by synchrotron radiation XRD, forexample.

The sulfide solid electrolyte material of the present invention does nothave a crystal phase B having a peak at a position of 2θ=30.12°±1.00° inX-ray diffraction measurement using a CuKα ray, or slightly has thecrystal phase B. The crystal phase B is considered to be a crystal phaseof argyrodite type. The crystal phase B generally has peaks at positionsof 2θ=15.60°, 18.04°, 25.60°, 30.12°, 31.46°, 45.26°, 48.16°, and52.66°. Incidentally, regarding these peak positions, a crystal latticeslightly changes due to factors such as the material composition, andthese peak positions occasionally shift in the range of ±1.00°. Aboveall, each peak position is preferably in the range of ±0.50°.

The ratios of the crystal phase A and the crystal phase B are notparticularly limited. When a diffraction intensity at the peak of thecrystal phase A (the peak in the vicinity of 2θ=29.58°) is designated asI_(A) and a diffraction intensity at the peak of the crystal phase B(the peak in the vicinity of 2θ=30.12°) is designated as I_(B), a valueof I_(B)/I_(A) is preferably smaller. The value of I_(B)/I_(A) isgenerally 0.6 or less, preferably 0.4 or less, more preferably 0.2 orless, and further preferably 0.1 or less.

Further, as described in Patent Literature 2, there is a possibilitythat a crystal phase having lower ion conductivity than the crystalphase A is precipitated when the crystal phase A is precipitated. Whenthis crystal phase is considered as a crystal phase C, the crystal phaseC generally has peaks of 2θ=17.46°, 18.12°, 19.99°, 22.73°, 25.72°,27.33°, 29.16°, and 29.78°. Incidentally, also these peak positionsoccasionally shift in the range of ±1.00°. Here, when a diffractionintensity at the peak of the crystal phase A (the peak in the vicinityof 2θ=29.58°) is designated as I_(A) and a diffraction intensity at thepeak of the crystal phase C (the peak in the vicinity of 2θ=27.33°) isdesignated as I_(C), a value of I_(C)/I_(A) is, for example, less than0.50, preferably 0.45 or less, more preferably 0.25 or less, furtherpreferably 0.15 or less, and particularly preferably 0.07 or less. Inaddition, the value of I_(C)/I_(A) is preferably 0. In other words, thesulfide solid electrolyte material of the present invention preferablydoes not have the crystal phase C.

The sulfide solid electrolyte material of the present invention isgenerally a crystalline sulfide solid electrolyte material. Further, thesulfide solid electrolyte material of the present invention ispreferably high in ion conductivity, and ion conductivity of the sulfidesolid electrolyte material at 25° C. is, for example, 2.1×10⁻³ S/cm ormore, preferably 3.4×10⁻³ S/cm or more, and more preferably 4.0×10⁻³S/cm or more. In addition, the shape of the sulfide solid electrolytematerial of the present invention is not particularly limited butexamples thereof may include a powdery shape. Further, the averageparticle diameter (D₅₀) of the powdery sulfide solid electrolytematerial is, for example, preferably in the range of 0.1 μm to 50 μm.

The sulfide solid electrolyte material of the present invention has highion conductivity and thus can be used for an arbitrary use in which ionconductivity is required. Above all, the sulfide solid electrolytematerial of the present invention is preferably used for a battery. Thereason for this is that the sulfide solid electrolyte material of thepresent invention can greatly contribute to achieving higher output of abattery. Further, a method for producing a sulfide solid electrolytematerial of the present invention will be described in detail in “C.Method for Producing Sulfide Solid Electrolyte Material” which will bedescribed later.

B. Battery

Next, the battery of the present invention will be described. FIG. 3 isa schematic cross-sectional view illustrating an example of a battery ofthe present invention. A battery 10 in FIG. 3 comprises a cathode activematerial layer 1 containing a cathode active material, an anode activematerial layer 2 containing an anode active material, an electrolytelayer 3 formed between the cathode active material layer 1 and the anodeactive material layer 2, a cathode current collector 4 for collectingcurrent by the cathode active material layer 1, an anode currentcollector 5 for collecting current by the anode active material layer 2,and a battery case 6 for accommodating these members. The presentinvention has a great feature in that at least one of the cathode activematerial layer 1, the anode active material layer 2, and the electrolytelayer 3 contains the sulfide solid electrolyte material described in theabove-described “A. Sulfide Solid Electrolyte Material.”

According to the present invention, when the above-described sulfidesolid electrolyte material is used, it is possible to obtain ahigh-output battery.

Hereinafter, each constitution of the battery of the present inventionwill be described.

1. Cathode Active Material Layer

The cathode active material layer in the present invention is a layerwhich contains at least a cathode active material. The cathode activematerial layer may contain at least one of a solid electrolyte material,a conductive material, and a binder, as necessary. In particular, in thepresent invention, the cathode active material layer contains a solidelectrolyte material and the solid electrolyte material is preferablythe above-described sulfide solid electrolyte material. The ratio of thesulfide solid electrolyte material contained in the cathode activematerial layer varies depending on the type of the battery. However, theratio of the sulfide solid electrolyte material is, for example, in therange of 0.1% by volume to 80% by volume, above all, preferably in therange of 1% by volume to 60% by volume and particularly preferably inthe range of 10% by volume to 50% by volume. Further, examples of thecathode active material may include LiCoO₂, LiMnO₂, Li₂NiMn₃O₈, LiVO₂,LiCrO₂, TIFePO₄, LiCoPO₄, LiNiO₂, and LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂.

The cathode active material layer may further contain a conductivematerial. When the conductive material is added, the conductivity of thecathode active material layer can be improved. Examples of theconductive material may include acetylene black, ketjen black, andcarbon fiber. Further, the cathode active material layer may contain abinder. As the type of the binder, for example, a fluoride-containingbinder such as polyvinylidene fluoride (PVDF) can be exemplified.Further, the thickness of the cathode active material layer is, forexample, preferably in the range of 0.1 μm to 1000 μm.

2. Anode Active Material Layer

The anode active material layer in the present invention is a layerwhich contains at least an anode active material. The anode activematerial layer may contain at least one of a solid electrolyte material,a conductive material, and a binder, as necessary. In particular, in thepresent invention, the anode active material layer contains a solidelectrolyte material and the solid electrolyte material is preferablythe above-described sulfide solid electrolyte material. The ratio of thesulfide solid electrolyte material contained in the anode activematerial layer varies depending on the type of the battery. However, theratio of the sulfide solid electrolyte material is, for example, in therange of 0.1% by volume to 80% by volume, above all, preferably in therange of 1% by volume to 60% by volume and particularly preferably inthe range of 10% by volume to 50% by volume. Further, examples of theanode active material may comprise a metal active material and a carbonactive material. Examples of the metal active material may include In,Al, Si, and Sn. Meanwhile, examples of the carbon active material mayinclude mesocarbon microbeads (MCMB), high orientation property graphite(HOPG), hard carbon, and soft carbon.

Incidentally, the conductive material and the binder used in the anodeactive material layer are the same as in the cathode active materiallayer described above. Further, the thickness of the anode activematerial layer is, for example, preferably in the range of 0.1 μm to1000 μm.

3. Electrolyte Layer

The electrolyte layer in the present invention is a layer formed betweenthe cathode active material layer and the anode active material layer.The electrolyte layer is not particularly limited as long as it is alayer in which ion conduction can be performed, but the layer ispreferably a solid electrolyte layer composed of a solid electrolytematerial. The reason for this is that a battery with high safety can beobtained as compared to the case of a battery using a liquidelectrolyte. Further, in the present invention, the solid electrolytelayer preferably contains the above-described sulfide solid electrolytematerial. The ratio of the sulfide solid electrolyte material containedin the solid electrolyte layer is preferably, for example, in the rangeof 10% by volume to 100% by volume, above all, in the range of 50% byvolume to 100% by volume. The thickness of the solid electrolyte layeris preferably, for example, in the range of 0.1 μm to 1000 μm, aboveall, in the range of 0.1 μm to 300 μm. Further, examples of a method forforming a solid electrolyte layer may include a method forcompression-molding a solid electrolyte material.

Further, the electrolyte layer in the present invention may be a layercomposed of a liquid electrolyte. In the case of using a liquidelectrolyte, a higher-output battery can be obtained although safetyneeds to be further considered as compared to the case of using a solidelectrolyte layer. In addition, in this case, generally, at least one ofthe cathode active material layer and the anode active material layercontains the above-described sulfide solid electrolyte material. Theliquid electrolyte generally contains a lithium salt and an organicsolvent (a non-aqueous solvent). Examples of the lithium salt mayinclude inorganic lithium salts such as LiPF₆, LiBF₄, LiClO₄, andLiAsF₆, and organic lithium salts such as LiCF₃SO₃, LiN(CF₃SO₂)₂,LiN(C₂F₅SO₂)₂, and LiC(CF₃SO₂)₃. Examples of the organic solvent mayinclude ethylene carbonate (EC), propylene carbonate (PC), dimethylcarbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC),and butylene carbonate (BC).

4. Other Constitutions

The battery of the present invention has at least the cathode activematerial layer, the anode active material layer, and the electrolytelayer which are described above. Further, the battery generally has acathode current collector for collecting current by the cathode activematerial layer and an anode current collector for collecting current bythe anode active material layer. Examples of a material of the cathodecurrent collector may include SUS, aluminum, nickel, iron, titanium, andcarbon. On the other hand, examples of a material of the anode currentcollector may include SUS, copper, nickel, and carbon. Furthermore, thethicknesses and shapes of the cathode current collector and the anodecurrent collector are preferably selected properly according to factorssuch as the use of the battery. Moreover, a battery case of a generalbattery can be used for a battery case used for the present invention.Examples of the battery case may include a battery case made of SUS.

5. Battery

The battery of the present invention may be a primary battery or asecondary battery. In particular, a secondary battery is preferablesince the secondary battery can be repeatedly charged and discharged andis useful as, for example, a battery mounted on a vehicle. Examples ofthe shape of the battery of the present invention may include a coinshape, a laminate shape, a barrel shape, and a square shape. Further, amethod for producing a battery of the present invention is notparticularly limited as long as it is a method by which theabove-described battery can be obtained, but the same method as a methodfor producing a general battery can be used. For example, in a casewhere the battery of the present invention is an all solid statebattery, examples of the producing method may include a method in whicha material composed of a cathode active material layer, a materialcomposed of a solid electrolyte layer, and a material composed of ananode active material layer are sequentially pressed to thereby producea power generating element, this power generating element isaccommodated inside a battery case, and the battery case is crimped.

C. Method for Producing Sulfide Solid Electrolyte Material

Next, a method for producing a sulfide solid electrolyte material of thepresent invention will be described. The method for producing a sulfidesolid electrolyte material of the present invention is a method forproducing the above-described sulfide solid electrolyte material and themethod comprises steps of: an ion conductive material synthesizing stepof synthesizing an amorphized ion conductive material by mechanicalmilling while using a raw material composition containing theconstitutional component of the sulfide solid electrolyte material, anda heating step of heating the amorphized ion conductive material toobtain the sulfide solid electrolyte material.

FIG. 4 is an explanatory diagram illustrating an example of a method forproducing a sulfide solid electrolyte material of the present invention.In the method for producing a sulfide solid electrolyte material in FIG.4, first, Li₂S, LiCl, P₂S₅, and SiS₂ are mixed to prepare a raw materialcomposition. At this time, in order to prevent the raw materialcomposition from deteriorating due to moisture in air, it is preferableto prepare a raw material composition under an inert gas atmosphere.Next, ball mill is performed for the raw material composition to obtainan amorphized ion conductive material. Subsequently, the amorphized ionconductive material is heated for improving the crystallinity to therebyobtain a sulfide solid electrolyte material.

According to the present invention, when amorphization is performed inthe ion conductive material synthesizing step and then the heating stepis performed, it is possible to obtain the sulfide solid electrolytematerial with favorable ion conductivity.

Hereinafter, the method for producing a sulfide solid electrolytematerial of the present invention will be described in each step.

1. Ion Conductive Material Synthesizing Step

The ion conductive material synthesizing step in the present inventionis a step of synthesizing an amorphized ion conductive material bymechanical milling while using a raw material composition containing theconstitutional component of the sulfide solid electrolyte material.

The raw material composition in the present invention contains at leasta Li element, a Si element, a P element, a S element, and an X element(X is at least one of F, Cl, Br, and I). Further, the raw materialcomposition may contain elements other than the above-describedelements. Examples of a compound containing the Li element may include asulfide of Li. Specific example of the sulfide of Li may include Li₂S.

Examples of a compound containing the Si element may include a simplesubstance of Si and a sulfide of Si. Specific examples of the sulfide ofSi may include SiS₂. Further, examples of a compound containing the Pelement may include a simple substance of P and a sulfide of P. Specificexamples of the sulfide of P may include P₂S₅. Examples of a compoundcontaining the X element may include LiX and LiPX₄. Further, regardingother elements used for the raw material composition, a simple substanceand sulfide thereof can be used.

The mechanical milling is a method for grinding a test sample whilemechanical energy is applied thereto. In the present invention, anamorphized ion conductive material is synthesized by applying mechanicalenergy to the raw material composition. Examples of such mechanicalmilling may include vibrating mill, ball mill, turbo mill,mechano-fusion, and disk mill; among them, vibrating mill and ball millare preferable.

The conditions of vibrating mill are not particularly limited as long asan amorphized ion conductive material can be obtained. The vibrationamplitude of vibrating mill is preferably, for example, in the range of5 mm to 15 mm, above all, in the range of 6 mm to 10 mm. The vibrationfrequency of vibrating mill is preferably, for example, in the range of500 rpm to 2000 rpm, above all, in the range of 1000 rpm to 1800 rpm.The filling factor of a test sample of vibrating mill is preferably, forexample, in the range of 1% by volume to 80% by volume, above all, inthe range of 5% by volume to 60% by volume, particularly, in the rangeof 10% by volume to 50% by volume. Further, a vibrator (for example, avibrator made of alumina) is preferably used for vibrating mill.

The conditions of ball mill are not particularly limited as long as anamorphized ion conductive material can be obtained. In general, largernumber of revolutions brings higher production rate of the ionconductive material, and longer treating time brings higher conversionratio of the raw material composition into the ion conductive material.The number of weighing table revolutions at the time of performingplanetary ball mill is preferably, for example, in the range of 200 rpmto 500 rpm, above all, in the range of 250 rpm to 400 rpm. Further, thetreating time at the time of performing planetary ball mill ispreferably, for example, in the range of 1 hour to 100 hours, above all,in the range of 1 hour to 70 hours.

2. Heating Step

The heating step in the present invention is a step of heating theamorphized ion conductive material to obtain the sulfide solidelectrolyte material.

The heating temperature in the present invention is not particularlylimited as long as it is a temperature at which a desired sulfide solidelectrolyte material can be obtained, but for example, the heatingtemperature is preferably 300° C. or higher, more preferably 350° C. orhigher, further preferably 400° C. or higher, and particularlypreferably 450° C. or higher. On the other hand, the heating temperatureis, for example, preferably 1000° C. or lower, more preferably 700° C.or lower, further preferably 650° C. or lower, and particularlypreferably 600° C. or lower. Further, the heating time is preferablyadjusted properly so as to obtain a desired sulfide solid electrolytematerial. In addition, heating in the present invention is preferablyperformed under an inert gas atmosphere or in a vacuum from theviewpoint of preventing oxidation. Further, the sulfide solidelectrolyte material obtained by the present invention is the same asthe contents described in the above-described “A. Sulfide SolidElectrolyte Material” and thus the description thereof is omitted.

Incidentally, the present invention is not limited to the embodimentsdescribed above. The above embodiments are merely an exemplification andany of those having substantially the same constitution as the technicalspirit described in Claims of the present invention and exhibiting thesame working effects as those is included in the technical scope of thepresent invention.

EXAMPLES

Hereinafter, the present invention will be described in more detail bymeans of Examples.

Example 1

Lithium sulfide (Li₂S, manufactured by Nippon Chemical Industrial CO.,LTD.), lithium chloride (LiCl, manufactured by Kojundo ChemicalLaboratory Co., Ltd.), phosphorus dipentasulfide (P₂S₅, manufactured byAldrich), and silicon sulfide (SiS₂, manufactured by JAPAN PURE CHEMICALCO., LTD.) were used as starting materials. Powders thereof were mixedin a glove box under an argon atmosphere at a ratio presented in thefollowing Table 1 to obtain a raw material composition. Next, 1 g of theraw material composition was put in a pot made of zirconia (45 ml)together with zirconia ball (10 mmϕ, 10 pieces) to hermetically seal thepot completely (an argon atmosphere). This pot was mounted on aplanetary ball milling machine (P7™ manufactured by FRITSCH JAPAN CO.,LTD.) to perform mechanical milling for 40 hours at the number ofweighing table revolutions of 370 rpm. Thus, an amorphized ionconductive material was obtained.

Next, powder of the obtained ion conductive material was put in acarbon-coated quartz tube and the quartz tube was vacuum-sealed. Thepressure of the quartz tube for vacuum-sealing was approximately 30 Pa.Next, the quartz tube was placed in a burning furnace, heated from roomtemperature to 475° C. over 6 hours, maintained at 475° C. for 8 hours,and thereafter slowly cooled up to room temperature. Thus, a sulfidesolid electrolyte material including a composition ofLi_(0.3)Si_(0.076)P_(0.05)S_(0.45)Cl_(0.3) was obtained.

Examples 2 to 54 and Comparative Examples 1 to 7

A sulfide solid electrolyte material was obtained in the same manner asin Example 1, except that the ratio of the raw material composition waschanged to the ratio presented in each of the following Table 1 andTable 2.

Examples 55 to 58

A sulfide solid electrolyte material was obtained in the same manner asin Example 1, except that lithium bromide (LiBr, manufactured by KojundoChemical Laboratory Co., Ltd.) was used instead of lithium chloride andthe ratio of the raw material composition was changed to the ratiopresented in the following Table 3.

[Evaluation]

(X-Ray Diffraction Measurement)

X-ray diffraction (XRD) measurement was performed using the sulfidesolid electrolyte material obtained in each of Examples 1 to 58 andComparative Examples 1 to 7. The XRD measurement was performed for apowder sample under an inert atmosphere on the condition of using a CuKαray. The representative results are shown in FIGS. 5A to 5C and FIGS. 6Aand 6B. As shown in FIG. 5A, in Example 7, a peak of the crystal phase Awas determined and a peak of the crystal phase B was not determined. Onthe other hand, as shown in FIGS. 5B and 5C, in Example 41 andComparative Example 4, peaks of the crystal phase A and the crystalphase B were determined, and the ratio of the crystal phase B inComparative Example 4 was larger than that in Example 41. Further, asshown in FIGS. 6A and 6B, in Example 7 and Example 55, a peak of thecrystal phase A was determined and a peak of the crystal phase B was notdetermined. In Example 7 and Example 55, the same peak was obtainedalthough the type of halogen is different. Further, I_(B)/I_(A) wasobtained from the result of the XRD measurement. The results thusobtained are presented in Table 1 to Table 3.

(Li Ion Conductance Measurement)

The Li ion conductance at 25° C. was measured using the sulfide solidelectrolyte material obtained in each of Examples 1 to 58 andComparative Examples 1 to 7. First, 200 mg of the sulfide solidelectrolyte material was weighed, put in a cylinder made of MACOR, andpressed at a pressure of 4 ton/cm². The both ends of the obtained pelletwere pinched with a pin made of SUS, and the confining pressure wasapplied to the pellet by fastening bolts, thereby obtaining a cell forevaluation. The Li ion conductance was calculated according to analternating-current impedance method while the cell for evaluation wasmaintained at 25° C. The measurement was performed using Solartron 1260™at an applied voltage of 5 mV and a measurement frequency range of 0.01to 1 MHz. The results thus obtained are presented in Table 1 to Table 3and FIG. 7.

TABLE 1 Li2S LiCl P2S5 SiS2 CONDUCTANCE (g) (g) (g) (g) x y z wI_(B)/I_(A) (S/cm) EXAMPLE 1 0.3793 0.04861 0.2849 0.3172 0.3889 0.07580.0505 0.0253 0.60 0.00270 EXAMPLE 2 0.3660 0.04966 0.2603 0.3240 0.38020.0781 0.0521 0.0280 0.07 0.00889 EXAMPLE 3 0.4172 0.02333 0.3058 0.25370.4048 0.0595 0.0595 0.0119 0.23 0.00516 EXAMPLE 4 0.4048 0.02383 0.31230.2591 0.3968 0.0613 0.0013 0.0123 0.14 0.00568 EXAMPLE 5 0.3918 0.024340.3191 0.2648 0.3884 0.0633 0.0633 0.0127 0.09 0.00649 EXAMPLE 6 0.38510.02461 0.3226 0.2677 0.3839 0.0643 0.0643 0.0129 0.06 0.00658 EXAMPLE 70.3783 0.02489 0.3262 0.2707 0.3794 0.0653 0.0653 0.0131 0 0.00659EXAMPLE 8 0.3927 0.04675 0.3064 0.2542 0.3976 0.0602 0.0602 0.0241 0.250.00892 EXAMPLE 9 0.3805 0.04768 0.3125 0.2593 0.3898 0.0620 0.06200.0248 0.08 0.00698 EXAMPLE 10 0.3678 0.04866 0.3189 0.2646 0.38160.0638 0.0638 0.0255 0.06 0.00513 EXAMPLE 11 0.3867 0.04604 0.31680.2504 0.3934 0.0596 0.0626 0.0238 0.16 0.00866 EXAMPLE 12 0.38100.04536 0.3270 0.2467 0.3894 0.0590 0.0649 0.0236 0.14 0.00513 EXAMPLE13 0.3877 0.04616 0.3025 0.2636 0.3940 0.0627 0.0597 0.0239 0.25 0.00859EXAMPLE 14 0.3829 0.04559 0.2988 0.2727 0.3905 0.0651 0.0592 0.0237 0.140.00984 EXAMPLE 15 0.3782 0.04503 0.2951 0.2816 0.3871 0.0674 0.05870.0235 0.10 0.00740 EXAMPLE 16 0.3737 0.04449 0.2916 0.2903 0.38370.0698 0.0581 0.0233 0.00 0.00716 EXAMPLE 17 0.3680 0.07026 0.30700.2547 0.3902 0.0610 0.0610 0.0366 0.62 0.00614 EXAMPLE 18 0.35620.07158 0.3127 0.2595 0.3827 0.0626 0.0626 0.0376 0.09 0.00647 EXAMPLE19 0.3439 0.07294 0.3187 0.2644 0.3748 0.0644 0.0644 0.0386 0.22 0.00387EXAMPLE 20 0.4049 0.03503 0.3061 0.2540 0.4012 0.0599 0.0599 0.0180 0.270.00655 EXAMPLE 21 0.3985 0.04670 0.2754 0.2793 0.4012 0.0659 0.05390.0240 0.60 0.00424 EXAMPLE 22 0.3863 0.04765 0.2810 0.2850 0.39350.0678 0.0555 0.0246 0.22 0.00874 EXAMPLE 23 0.3736 0.04863 0.28690.2909 0.3853 0.0698 0.0571 0.0254 0.07 0.00839 EXAMPLE 24 0.37400.07018 0.2760 0.2799 0.3939 0.0667 0.0545 0.0364 0.29 0.00458 EXAMPLE25 0.4113 0.02335 0.3367 0.2286 0.4012 0.0539 0.0659 0.0120 0.22 0.00530EXAMPLE 26 0.3868 0.04680 0.3374 0.2291 0.3939 0.0545 0.0667 0.0242 0.230.00702 EXAMPLE 27 0.3990 0.03507 0.3371 0.2288 0.3976 0.0542 0.06630.0181 0.19 0.00595 EXAMPLE 28 0.4210 0 0.2901 0.2889 0.3982 0.06810.0567 0 0.07 0.00394 EXAMPLE 29 0.4100 0.02381 0.2837 0.2825 0.40000.0666 0.0555 0.0122 0.35 0.00480 EXAMPLE 30 0.3970 0.02433 0.28990.2887 0.3916 0.0887 0.0572 0.0126 0.11 0.00866

TABLE 2 Li2S LiCl P2S5 SiS2 CONDUCTANCE (g) (g) (g) (g) x y z wI_(B)/I_(A) (S/cm) EXAMPLE 31 0.3834 0.02488 0.2965 0.2952 0.3827 0.07090.0591 0.0130 0 0.00652 EXAMPLE 32 0.3979 0.03572 0.2838 0.2826 0.39660.0699 0.0558 0.0184 0.27 0.00521 EXAMPLE 33 0.3850 0.03649 0.28980.2886 0.3883 0.0690 0.0575 0.0190 0.09 0.00707 EXAMPLE 34 0.37160.03729 0.2962 0.2949 0.3795 0.0712 0.0593 0.0196 0.05 0.00598 EXAMPLE35 0.3857 0.05843 0.2785 0.2773 0.3973 0.0658 0.0548 0.0301 0.58 0.00710EXAMPLE 36 0.3737 0.05958 0.2840 0.2828 0.3896 0.0676 0.0563 0.0310 0.160.00662 EXAMPLE 37 0.3611 0.06078 0.2897 0.2885 0.3816 0.0696 0.05800.0319 0.12 0.00571 EXAMPLE 38 0.3480 0.06202 0.2956 0.2944 0.37300.0717 0.0597 0.0329 0.10 0.00453 EXAMPLE 39 0.3902 0.04331 0.28380.2827 0.3944 0.0671 0.0559 0.0224 0.22 0.00643 EXAMPLE 40 0.38390.04376 0.2868 0.2856 0.3904 0.0681 0.0568 0.0227 0.17 0.00893 EXAMPLE41 0.4195 0.01330 0.2720 0.2951 0.4022 0.0693 0.0530 0.0068 0.37 0.00303EXAMPLE 42 0.3857 0.02666 0.3005 0.2871 0.3850 0.0688 0.0598 0.0139 00.00878 EXAMPLE 43 0.3518 0.04007 0.3292 0.2789 0.3670 0.0683 0.06690.0213 0.42 0.00235 EXAMPLE 44 0.3688 0.03336 0.3148 0.2830 0.37610.0685 0.0633 0.0176 0 0.00812 EXAMPLE 45 0.4090 0.01333 0.3276 0.25010.3957 0.0592 0.0644 0.0069 0.11 0.00542 EXAMPLE 46 0.3763 0.026710.3501 0.2469 0.3789 0.0598 0.0702 0.0140 0.18 0.00533 EXAMPLE 47 0.39050.02664 0.2758 0.3071 0.3880 0.0733 0.0546 0.0138 0.11 0.00447 EXAMPLE48 0.3560 0.04004 0.3075 0.2965 0.3697 0.0723 0.0622 0.0212 0 0.00545EXAMPLE 49 0.4143 0.01332 0.2988 0.2726 0.3990 0.0643 0.0587 0.0068 0.170.00512 EXAMPLE 50 0.3810 0.02668 0.3253 0.2670 0.3820 0.0642 0.06490.0140 0 0.00640 EXAMPLE 51 0.3977 0.01999 0.3125 0.2698 0.3906 0.06430.0618 0.0104 0.10 0.00630 EXAMPLE 52 0.3644 0.03339 0.3381 0.26420.3732 0.0642 0.0682 0.0177 0.30 0.00342 EXAMPLE 53 0.3919 0.057400.3010 0.2497 0.4012 0.0590 0.0590 0.0295 0.10 0.00755 EXAMPLE 54 0.36320.09654 0.2953 0.2450 0.3972 0.0583 0.0583 0.0500 0.35 0.00803COMPARATIVE 0.3562 0.07042 0.3692 0.2042 0.3827 0.0494 0.0741 0.03700.99 0.00179 EXAMPLE 1 COMPARATIVE 0.3716 0.04965 0.2278 0.3510 0.38380.0842 0.0453 0.0259 3.15 0.00034 EXAMPLE 2 COMPARATIVE 0.3576 0.050760.2329 0.3588 0.3746 0.0870 0.0468 0.0268 0.72 0.00165 EXAMPLE 3COMPARATIVE 0.3621 0.07034 0.3381 0.2295 0.3865 0.0552 0.0675 0.03680.86 0.00171 EXAMPLE 4 COMPARATIVE 0.4071 0 0.2970 0.2958 0.3890 0.07040.0587 0 6.92 0.00049 EXAMPLE 5 COMPARATIVE 0.3765 0.09453 0.2891 0.23990.4052 0.0566 0.0566 0.0485 0.60 0.00105 EXAMPLE 6 COMPARATIVE 0.4299 00.3670 0.2030 0.4048 0.0476 0.0714 0 0 0.00200 EXAMPLE 7

TABLE 3 Li2S LiBr P2S5 SiS2 CONDUCTANCE (g) (g) (g) (g) x y z wI_(B)/I_(A) (S/cm) EXAMPLE 55 0.3607 0.08657 0.2770 0.2758 0.3862 0.06920.0576 0.0231 0 0.00865 EXAMPLE 56 0.3871 0.04861 0.2827 0.2815 0.39160.0687 0.0572 0.0126 0 0.00611 EXAMPLE 57 0.3797 0.04966 0.2542 0.31640.3866 0.0776 0.0517 0.0129 0 0.00829 EXAMPLE 58 0.3609 0.09475 0.24250.3018 0.3889 0.0758 0.0505 0.0253 0 0.00702

As shown in Table 1 to Table 3 and FIG. 7, the Li ion conductance inExamples 1 to 58 was higher than that in Comparative Examples 1 to 7. Inparticular, in Comparative Examples 6 and 7, although I_(B)/I_(A)≤0.6was satisfied, the compositional range deviated and thus the Li ionconductance became lower. Meanwhile, the relation between I_(B)/I_(A)and Li ion conductance is shown in FIG. 8. As shown in FIG. 8, it wasconfirmed that in the compositional range of the present invention, asthe value of I_(B)/I_(A) decreases, the Li ion conductance is improved.

REFERENCE SIGNS LIST

-   1 Cathode active material layer-   2 Anode active material layer-   3 Electrolyte layer-   4 Cathode current collector-   5 Anode current collector-   6 Battery case-   10 Battery

What is claimed is:
 1. A sulfide solid electrolyte material comprising acomposition of:Li_(x)Si_(y)P_(z)S_(1-x-y-z-w)Cl_(w) where: 0.3697≤x≤0.4048,0.0539≤y≤0.0781, 0.0521≤z≤0.0702, and 0≤w≤0.05, wherein: the sulfidesolid electrolyte material has a crystal phase A having a peak at aposition of 2θ=20.18°±1.00° and 29.58°±1.00° in X-ray diffractionmeasurement using a CuKα ray, and the sulfide solid electrolyte materialdoes not have a crystal phase B having a peak at a position of2θ=15.60°±1.00° and 30.12°±1.00° in X-ray diffraction measurement usinga CuKα ray, or in a case where the sulfide solid electrolyte materialhas the crystal phase B, when a diffraction intensity at the peak of2θ=29.58°±1.00° is designated as I_(A) and a diffraction intensity atthe peak of 2θ=30.12°±1.00° is designated as I_(B), a value ofI_(B)/I_(A) is 0.6 or less.
 2. A battery comprising: a cathode activematerial layer containing a cathode active material; an anode activematerial layer containing an anode active material; and an electrolytelayer formed between the cathode active material layer and the anodeactive material layer, wherein at least one of the cathode activematerial layer, the anode active material layer, and the electrolytelayer comprises the sulfide solid electrolyte material according toclaim
 1. 3. The sulfide solid electrolyte material according to claim 1,wherein: 0.3802≤x≤0.4012, 0.054≤y≤0.078, 0.0521≤z≤0.0667, and0.0126≤w≤0.05.
 4. A sulfide solid electrolyte material comprising acomposition ofLi_(x)Si_(y)P_(z)S_(1-x-y-z-w)Br_(w), where: 0.3862≤x≤0.3916,0.0687≤y≤0.0776, 0.0505≤z≤0.0576, and 0.0126≤w≤0.0253, wherein thesulfide solid electrolyte material has a crystal phase A having a peakat a position of 2θ=20.18°±1.00° and 29.58°±1.00° in X-ray diffractionmeasurement using a CuKα ray, and the sulfide solid electrolyte materialdoes not have a crystal phase B having a peak at a position of2θ=15.60°±1.00° and 30.12°±1.00° in X-ray diffraction measurement usinga CuKα ray.
 5. A battery comprising: a cathode active material layercontaining a cathode active material; an anode active material layercontaining an anode active material; and an electrolyte layer formedbetween the cathode active material layer and the anode active materiallayer, wherein at least one of the cathode active material layer, theanode active material layer, and the electrolyte layer contains thesulfide solid electrolyte material according to claim
 4. 6. A method forproducing the sulfide solid electrolyte material according to claim 4,the method comprising: synthesizing an amorphized ion conductivematerial by mechanical milling while using a raw material compositioncontaining a constitutional component of the sulfide solid electrolytematerial; and heating the amorphized ion conductive material to obtainthe sulfide solid electrolyte material.